Thursday, July 29, 2010

Dengue and dengue haemorrhagic fever

Key facts

Dengue is a mosquito-borne infection that causes a severe flu-like illness, and sometimes a potentially lethal complication called dengue haemorrhagic fever.

Global incidence of dengue has grown dramatically in recent decades.

About two fifths of the world's population are now at risk.

Dengue is found in tropical and sub-tropical climates worldwide, mostly in urban and semi-urban areas.

Dengue haemorrhagic fever is a leading cause of serious illness and death among children in some Asian countries.

There is no specific treatment for dengue, but appropriate medical care frequently saves the lives of patients with the more serious dengue haemorrhagic fever.

The only way to prevent dengue virus transmission is to combat the disease-carrying mosquitoes.

Dengue is a mosquito-borne infection that in recent decades has become a major international public health concern. Dengue is found in tropical and sub-tropical regions around the world, predominantly in urban and semi-urban areas.

Dengue haemorrhagic fever (DHF), a potentially lethal complication, was first recognized in the 1950s during dengue epidemics in the Philippines and Thailand. Today DHF affects most Asian countries and has become a leading cause of hospitalization and death among children in the region.

There are four distinct, but closely related, viruses that cause dengue. Recovery from infection by one provides lifelong immunity against that virus but confers only partial and transient protection against subsequent infection by the other three viruses. There is good evidence that sequential infection increases the risk of developing DHF.

Global burden of dengue

The incidence of dengue has grown dramatically around the world in recent decades. Some 2.5 billion people – two fifths of the world's population – are now at risk from dengue. WHO currently estimates there may be 50 million dengue infections worldwide every year.

In 2007 alone, there were more than 890 000 reported cases of dengue in the Americas, of which 26 000 cases were DHF.

The disease is now endemic in more than 100 countries in Africa, the Americas, the Eastern Mediterranean, South-east Asia and the Western Pacific. South-east Asia and the Western Pacific are the most seriously affected. Before 1970 only nine countries had experienced DHF epidemics, a number that had increased more than four-fold by 1995.

Not only is the number of cases increasing as the disease is spreading to new areas, but explosive outbreaks are occurring. In 2007, Venezuela reported over 80 000 cases, including more than 6 000 cases of DHF.

Some other statistics:

During epidemics of dengue, infection rates among those who have not been previously exposed to the virus are often 40% to 50%, but can reach 80% to 90%.

An estimated 500 000 people with DHF require hospitalization each year, a very large proportion of whom are children. About 2.5% of those affected die.

Without proper treatment, DHF fatality rates can exceed 20%. Wider access to medical care from health providers with knowledge about DHF - physicians and nurses who recognize its symptoms and know how to treat its effects - can reduce death rates to less than 1%.

The spread of dengue is attributed to expanding geographic distribution of the four dengue viruses and their mosquito vectors, the most important of which is the predominantly urban species Aedes aegypti. A rapid rise in urban mosquito populations is bringing ever greater numbers of people into contact with this vector, especially in areas that are favourable for mosquito breeding, e.g. where household water storage is common and where solid waste disposal services are inadequate.

Transmission

WHO/TDR/Stammers

Dengue viruses are transmitted to humans through the bites of infective female Aedes mosquitoes. Mosquitoes generally acquire the virus while feeding on the blood of an infected person. After virus incubation for eight to 10 days, an infected mosquito is capable, during probing and blood feeding, of transmitting the virus for the rest of its life. Infected female mosquitoes may also transmit the virus to their offspring by transovarial (via the eggs) transmission, but the role of this in sustaining transmission of the virus to humans has not yet been defined.

Infected humans are the main carriers and multipliers of the virus, serving as a source of the virus for uninfected mosquitoes. The virus circulates in the blood of infected humans for two to seven days, at approximately the same time that they have a fever; Aedes mosquitoes may acquire the virus when they feed on an individual during this period. Some studies have shown that monkeys in some parts of the world play a similar role in transmission.

Characteristics

Dengue fever is a severe, flu-like illness that affects infants, young children and adults, but seldom causes death.

The clinical features of dengue fever vary according to the age of the patient. Infants and young children may have a fever with rash. Older children and adults may have either a mild fever or the classical incapacitating disease with abrupt onset and high fever, severe headache, pain behind the eyes, muscle and joint pains, and rash.

Dengue haemorrhagic fever (DHF) is a potentially deadly complication that is characterized by high fever, often with enlargement of the liver, and in severe cases circulatory failure. The illness often begins with a sudden rise in temperature accompanied by facial flush and other flu-like symptoms. The fever usually continues for two to seven days and can be as high as 41°C, possibly with convulsions and other complications.

In moderate DHF cases, all signs and symptoms abate after the fever subsides. In severe cases, the patient's condition may suddenly deteriorate after a few days of fever; the temperature drops, followed by signs of circulatory failure, and the patient may rapidly go into a critical state of shock and die within 12 to 24 hours, or quickly recover following appropriate medical treatment (see below).

Treatment

There is no specific treatment for dengue fever.

For DHF, medical care by physicians and nurses experienced with the effects and progression of the complicating haemorrhagic fever can frequently save lives - decreasing mortality rates from more than 20% to less than 1%. Maintenance of the patient's circulating fluid volume is the central feature of DHF care.

Immunization

There is no vaccine to protect against dengue. Although progress is underway, developing a vaccine against the disease - in either its mild or severe form - is challenging.

With four closely related viruses that can cause the disease, the vaccine must immunize against all four types to be effective.

There is limited understanding of how the disease typically behaves and how the virus interacts with the immune system.

There is a lack of laboratory animal models available to test immune responses to potential vaccines.

Despite these challenges, two vaccine candidates have advanced to evaluation in human subjects in countries with endemic disease, and several potential vaccines are in earlier stages of development. WHO provides technical advice and guidance to countries and private partners to support vaccine research and evaluation.

Prevention and control

At present, the only method of controlling or preventing dengue virus transmission is to combat the vector mosquitoes.

In Asia and the Americas, Aedes aegypti breeds primarily in man-made containers like earthenware jars, metal drums and concrete cisterns used for domestic water storage, as well as discarded plastic food containers, used automobile tyres and other items that collect rainwater. In Africa the mosquito also breeds extensively in natural habitats such as tree holes, and leaves that gather to form "cups" and catch water.

WHO/TDR/Crump

In recent years, Aedes albopictus, a secondary dengue vector in Asia, has become established in the United States, several Latin American and Caribbean countries, parts of Europe and Africa. The rapid geographic spread of this species is largely attributed to the international trade in used tyres, a breeding habitat.

Vector control is implemented using environmental management and chemical methods. Proper solid waste disposal and improved water storage practices, including covering containers to prevent access by egg-laying female mosquitoes are among methods that are encouraged through community-based programmes.

The application of appropriate insecticides to larval habitats, particularly those that are useful in households, e.g. water storage vessels, prevents mosquito breeding for several weeks but must be re-applied periodically. Small, mosquito-eating fish and copepods (tiny crustaceans) have also been used with some success.

During outbreaks, emergency vector control measures can also include broad application of insecticides as space sprays using portable or truck-mounted machines or even aircraft. However, the mosquito-killing effect is transient, variable in its effectiveness because the aerosol droplets may not penetrate indoors to microhabitats where adult mosquitoes are sequestered, and the procedure is costly and operationally difficult. Regular monitoring of the vectors' susceptibility to widely used insecticides is necessary to ensure the appropriate choice of chemicals. Active monitoring and surveillance of the natural mosquito population should accompany control efforts to determine programme effectiveness. (http://www.who.int/mediacentre/factsheets/fs117/en/)

Dengue fever cases on rise in Philippines

MANILA, Philippines, July 26 (UPI) -- At least 23 people, mostly children, have died of mosquito-borne dengue fever in the Philippines since the start of the year, health officials said.

Health officials in Zamboanga City say the disease, which has stricken 1,052 others in the same period, is a cause for alarm, the Philippine Daily Inquirer reported Sunday.

"It has reached the alert level in Western Mindanao. The number of deaths is higher compared to 2008, during which we declared a dengue outbreak with eight deaths," Rodelin Agbulos said.

Officials have started a cleanup drive in the wake of a nearly 300 percent rise in dengue cases in some areas.

Common breeding sites of mosquitoes were old boats, bamboo posts, old motorcycle tires, shells and vegetation growth, the provincial health office said.

Community groups and residents were working to remove or clean up these possible breeding places of the Aedes aegypti, the day-breeding mosquito that causes dengue fever, the Inquirer reported. (http://www.upi.com/Science_News/2010/07/26/Dengue-fever-cases-on-rise-in-Philippines/UPI-39021280177785/)

Boredom May Be DeadlyBored people may be more likely to die early, according to English researchers.They studied the responses collected between 1985 and 1988 from more than 7,500 London civil servants, ages 35 to 55, who were asked if they had felt bored at work during the previous month, the Associated Press reported.When they looked at how many of the participants had died by April 2009, the University College London researchers found that those who said they had been very bored at work were 2.5 times more likely to have died of a heart problem than those who were bored. This increased risk was reduced when the researchers adjusted for other potential risk factors, such as fitness levels.Boredom alone isn't likely to be dangerous, but it could be associated with risk factors such as smoking, drinking, using drugs or psychological problems, said the researchers, the AP reported.The article will be published in the April issue of the International Journal of Epidemiology.

Thursday, July 15, 2010

The human brain has amazed and baffled people throughout the ages. Some scientists and doctors have devoted their entire lives to learning how the brain works. It is no wonder that people enjoy learning facts about this incredible organ in the human body. Below, you will find 100 facts about the brain including how it works, how it develops, what it controls, how it affects sleep, dreams, and memory, and more, which may be helpful. When you finish reading about these fun facts, take this short brainpower quiz and see how much you learned about the human brain.Physical Attributes
These facts will teach you interesting bits of information about the physical make-up of the human brain.

Weight. The weight of the human brain is about 3 lbs.

Cerebrum. The cerebrum is the largest part of the brain and makes up 85% of the brain’s weight.

Skin. Your skin weighs twice as much as your brain.

Gray matter. The brain’s gray matter is made up of neurons, which gather and transmit signals.

White matter. The white matter is made up of dendrites and axons, which create the network by which neurons send their signals.

Gray and white. Your brain is 60% white matter and 40% gray matter.

Water. The brain is made up of about 75% water.

Neurons. Your brain consists of about 100 billion neurons.

Synapses. There are anywhere from 1,000 to 10,000 synapses for each neuron.

No pain. There are no pain receptors in the brain, so the brain can feel no pain.

Largest brain. While an elephant’s brain is physically larger than a human brain, the human brain is 2% of total body weight (compared to 0.15% of an elephant’s brain), meaning humans have the largest brain to body size.

Love hormones and autism. Oxytocin, one of the hormones responsible for triggering feelings of love in the brain, has shown some benefits to helping control repetitive behaviors in those with autism.

Food and intelligence. A study of one million students in New York showed that students who ate lunches that did not include artificial flavors, preservatives, and dyes did 14% better on IQ tests than students who ate lunches with these additives.

Seafood. In the March 2003 edition of Discover magazine, a report describes how people in a 7-year study who ate seafood at least one time every week had a 30% lower occurrence of dementia.

Psychology of the Brain
From tickling to tasting to decision-making, find out how the brain affects what you experience.

Imaginary playmates. A study from Australia showed that children with imaginary playmates between the ages of 3 and 9 tended to be first-born children.

Reading faces. Without any words, you may be able to determine if someone is in a good mood, is feeling sad, or is angry just by reading the face. A small area in the brain called the amygdala is responsible for your ability to read someone else’s face for clues to how they are feeling.

Ringing in the ears. For years, medical professionals believed that tinnitus was due to a function within the mechanics of the ear, but newer evidence shows that it is actually a function of the brain.

Supertasters. There is a class of people known as supertasters who not only have more taste buds on the tongue, but whose brain is more sensitive to the tastes of foods and drinks. In fact, they can detect some flavors that others cannot.

Cold. Some people are much more sensitive to cold and actually feel pain associated with cold. Research as shown that the reason is due to certain channels that send cold information to the brain.

Decision-making. Women tend to take longer to make a decision, but are more likely to stick with the decision, compared to men, who are more likely to change their mind after making a decision.

Exercise. Some studies indicate that while some people are naturally more active, others are naturally more inactive, which may explain why getting out and exercising is more difficult for some.

Boredom. Boredom is brought on by a lack of change of stimulation, is largely a function of perception, and is connected to the innate curiosity found in humans.

Physical illness. The connection between body and mind is a strong one. One estimate is that between 50-70% of visits to the doctor for physical ailments are attributed to psychological factors.

Sadness and shopping. Researchers have discovered that those experiencing the blues are more willing to spend more money in an attempt to alleviate their sadness.

Memory
Learn how scent, jet lag, and estrogen affect memory, plus plenty of other information, with these facts.

Nightly average. Most people dream about 1-2 hours a night and have an average of 4-7 dreams each night.

Brain waves. Studies show that brain waves are more active while dreaming than when you are awake.

Lost dreams. Five minutes after a dream, half of the dream is forgotten. Ten minutes after a dream, over 90% is forgotten. Write down your dreams immediately if you want to remember them.

Blind people dream. Dreams are more than just visual images, and blind people do dream. Whether or not they dream in pictures depends on if they were born blind or lost their vision later.

Color or B&W. Some people (about 12%) dream only in black and white while others dream in color.

Virtually paralyzed. While you sleep, your body produces a hormone that may prevent you from acting out your dreams, leaving you virtually paralyzed.

Snoring. If you are snoring, you are not dreaming.

During a dream. If you are awakened during a dream, you are much more likely to remember the dream than if you slept until a full night’s sleep.

Symbolism. As those who invest in dream dictionaries can attest, dreams almost never represent what they actually are. The unconscious mind strives to make connections with concepts you will understand, so dreams are largely symbolic representations.

Adenosine. Caffeine works to block naturally occurring adenosine in the body, creating alertness. Scientists have recently discovered this connection and learned that doing the opposite–boosting adenosine–can actually help promote more natural sleep patterns and help eliminate insomnia.

Dream showings. Japanese researchers have successfully developed a technology that can put thoughts on a screen and may soon be able to screen people’s dreams.

Fun and Interesting Facts
From juggling to a Brain Bank to cannibalism, read about these fun and interesting brain facts.

Airplanes and headaches. A study showed a correlation between flying and headaches and states that around 6% of people who fly get headaches brought on by the flight itself.

Juggling. Juggling has shown to change the brain in as little as seven days. The study indicates that learning new things helps the brain to change very quickly.

Thoughts. The average number of thoughts that humans are believed to experience each day is 70,000.

Ambidexterity. Those who are left-handed or ambidextrous have a corpus collosum (the part of the brain that bridges the two halves) that is about 11% larger than those who are right-handed.

Stressful job. According to a study by Bristol-Myers Squibb, accountants have the highest incidence of on-the-job headaches, followed by librarians, then bus and truck drivers.

Aristotle. Aristotle mistakenly thought that the functions of the brain actually took place in the heart.

Cannibalism. Some research shows that humans carry genes that help protect the brain from prion diseases, or diseases contracted through eating human flesh, leading medical experts to believe that ancient humans may have eaten other humans.

Shakespeare. The word "brain" appears 66 times in the plays of William Shakespeare.

Famous Brains
People have always been fascinated with the brains of famous people. Find out what experts know about these famous brains.

Albert Einstein. Einstein’s brain was similar in size to other humans except in the region that is responsible for math and spatial perception. In that region, his brain was 35% wider than average.

London taxi drivers. Famous for knowing all the London streets by heart, these drivers have a larger than normal hippocampus, especially the drivers who have been on the job longest. The study suggests that as people memorize more and more information, this part of their brain continues to grow.

Daniel Tammet. Daniel Tammet is an autistic savant who, since the age of three when he suffered an epileptic seizure, has been able to perform astounding mathematical computations, knows seven languages, and is developing a language of his own.